An evanescent-field sensor system and method of using the system to detect either liquid- or airborne biological pathogens, chemical agents, and other harmful or toxic species is provided. Each of the plurality of intermediate components has a uniform inner surface, although at least two of the plurality of intermediate components having distinct outer surfaces. The guide insert may include a base flange, a pair of side flanges for funneling product units into the truncated area that defines a next dispensing position. Then, the estimated noise energy is subtracted from the noisy speech energy to obtain estimated clean speech energy. The rotor inertia belt member includes an extraction air cavity. The eyepiece lens system has satisfactory telecentricity on the object side and satisfactorily corrects aberration.